The present invention relates generally to lighting devices with dimming control. More particularly, the present invention relates to a light-emitting diode (LED) driver configured to improve low LED current stability by applying an adaptive hysteresis dimming reference control method.
Most LED drivers have a very wide range of output current control capability or very low dimming capability including, for example, a 1.5 A to 1 mA output current range. For certain conventional driver configurations, low-frequency noise or other minor perturbations can cause instability at relatively low dimming output currents, further resulting in flickering that is unacceptable for many LED lighting applications. LED drivers are particularly susceptible to “ripple” noise components that are residual from AC-DC rectification of an AC mains input. While the presence of such ripple components is not substantive at higher output current levels, they can be proportionately significant at lower (dimmed) output levels.